Biodisinfestation for Meloidogyne and Verticillium control in commercial protected crops in the Basque Country Atlantic area (northern Spain)

Biodisinfestation with organic amendments has been used infrequently for soil disease management of protected crops in the Basque Country (northern Spain). The temperate-humid climate has obstructed the application of biosolarization, very extended in Mediterranean horticultural areas such as South-eastern Spain. However, previous experimentation with different amendments, doses and application times compatible with crop cycles showed the applicability of these practices in this climate region. The above-mentioned techniques have begun to be applied in commercial greenhouses. The first commercial greenhouse presented persistent problems of root-knot nematodes in a tomato crop. Three soil disinfestation treatments (Raphanus sativus green manure combined with fresh animal manure and plastic mulch; Fresh animal manure and plastic mulch; Control (non-amended and non-mulched soil) were factorially combined with two grafting treatments (Grafted (intermediate resistant cultivar 'King-Kong'); Non-grafted (susceptible cultivar 'Jack')). Amendments were incorporated on spring and remained sealed for 26 days with black plastic mulch before planting. At 53 days after transplant (DAT), manure and plastic increased plant height by 11% compared to control soil treatment but only in grafted plants (P-value = 0.0108 for soil x grafting interaction). At 145 DAT, the R. sativus + manure + plastic treatment showed a significantly lower root nematode index than the control treatment (31% reduction for non-grafted plants, 19% for grafted plants and 38% for the average) but not the manure + plastic treatment (14% reduction for non-grafted, -19% for grafted, 14% for average). Surprisingly, the nematode index was 25% higher in the grafted plants than non-grafted plants. In a second commercial greenhouse with increasing problems of Verticillium wilt in a pepper crop (susceptible cultivar 'Derio'), biosolarization for 70 days using fresh manure with transparent polyethylene plastic reduced disease incidence (from 25-17% to 0.1-0.3%). These positive results are an incentive for the progressive implementation of these practices on a commercial scale.